Our objective is to understand observed human fertility behavior. We propose to develop a unified economic framework from which we will derive and subject to empirical test refutable hypotheses about fertility patterns in the United States. The framework rests heavily on recent advances in the economic theory of human capital and the allocation of time. The analytical structure is distinguished by four characteristics: (1) households are the primary focus of analysis, (2) households are viewed as engaging in productive activities within the home utilizing their available time resources in combination with market goods, (3) individual members of the household invest in "human capital" which enhances the productivity of their time in market and home-production activities, and (4) households are motivated to organize their activities in a way which economizes their scarce time resource. This analytical framework will be applied to observed human behavior regarding completed fertility, fertility control and the timing and spacing of births using both comparative-static equilibrium models and dynamic life cycle models. Single and simultaneous equation econometric methods of estimation will be applied to numerous national cross-section surveys of household behavior.